Integrated circuit device

ABSTRACT

An integrated circuit device having a semiconductor device and an encapsulating material on at least a portion of the semiconductor device and a method for encapsulating an integrated circuit device is disclosed. The encapsulating material includes a plurality of nanoparticles.

FIELD OF THE INVENTION

The present invention relates to encapsulation materials. Moreparticularly, the present invention relates to encapsulation materialsthat include a plurality of nanoparticles.

BACKGROUND OF THE INVENTION

Integrated circuit devices are commonly encapsulated to protect themfrom environmental hazards such as air, moisture, chemicals, and light,and to provide the integrated circuit with greater physical strength.Useful encapsulating materials include ceramics and polymers. Generally,encapsulating polymers include, for example, epoxies. Epoxies caninclude epoxy resins and thermosetting epoxy resins.

Integrated circuit devices include, for example semiconductor devicesused in various electronic devices and optical devices. Thesemiconductor device can include many integrated circuit materials suchas, at least one metal region, i.e., a metal line, bonding pad, and leadframe, at least one doped region, and at least one insulator layerformed on or in a semiconductor substrate. The semiconductor substrateis sometimes called a die. Often, the semiconductor device includes aheat sink.

Heat generated during operation can cause the integrated circuitmaterials to expand and/or contract. The amount that each integratedcircuit material expands and/or contracts can be described by thecoefficient of thermal expansion (“CTE”) of the particular material. Anddifferent materials have different CTE's. Composite materials,comprising one or more particular material, can expand and/or contractin volume and/or area as well. The expansion of the composite materialcan be described by the thermal expansion (“TE”) of the composite. TheCTE's of the particular materials making up the composite can becombined in various ways, depending on the composite material inquestion, to yield a TE for the composite. For example, in someinstances the TE of the composite can be a weighted average of the CTE'sof each particular material in the composite. However, in otherinstances the CTE's of the particular materials making up the compositecombine in other ways to yield the TE for the composite.

Problems often arise in integrated circuit devices, however, when the TEof materials making up the integrated circuit differ. One problem occursat the interface of the semiconductor device and the encapsulatingmaterial. In particular, the thermal expansion of the semiconductordevice (“TE_(SD)”) and the thermal expansion of the encapsulatingmaterial (“TE_(EM)”) are not the same. As a result, these materialsexpand to different extents during operation and this can cause stressat the interface of these two materials. This stress often leads tocracking of the encapsulating material.

Accordingly, it would be useful to be able to match the TE_(SD) to theTE_(EM) to prevent stress and reduce the negative effects of the stress.

SUMMARY OF THE INVENTION

In an embodiment of the invention, there is an integrated circuit devicehaving a semiconductor device and an encapsulating material on at leasta portion of the semiconductor device. The encapsulating materialincludes a plurality of nanoparticles.

In another embodiment of the invention, there is an integrated circuitencapsulating material having an epoxy and a plurality of nanoparticles.The plurality of nanoparticles can be dispersed in the epoxy.

In another embodiment of the invention, there is a method ofencapsulating an integrated circuit device. The method includesproviding a semiconductor device and contacting the semiconductor devicewith the encapsulant material. In this embodiment, the encapsulantmaterial includes a plurality of nanoparticles.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of theinvention and together with the description, serve to explain theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an exemplary semiconductor package in accordance with anembodiment of the invention.

FIG. 2A depicts an exemplary section of an encapsulation materialincluding a plurality of nanoparticles.

FIG. 2B depicts another exemplary section of an encapsulation materialincluding a plurality of coated nanoparticles.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

In an embodiment of the invention, there is an integrated circuit devicecomprising a semiconductor device. The semiconductor device can includemany integrated circuit materials such as metals, insulators, andsemiconductors. Metal regions can be formed in or on a semiconductorsubstrate to form metal lines, bonding pads, interconnects, and leadframes. Certain metal regions can be used to dissipate heat generatedduring operation. Metals can include, for example, Ti, W, Al, Mo, Pt,Cu, Ag, Ag, and other materials known to one of skill in the art.

As mentioned, the integrated circuit materials may also includeinsulator layers. Insulators often form layers on or in a semiconductorsubstrate. Examples of insulator materials include oxides and nitrides.Additionally, examples of semiconductor substrate materials includesilicon, SiGe, GaAs, AlGaAs, SiC, AInGaP, InP, and other materials thatwill be well known to practitioners in the art.

The different materials used in the integrated circuit can be patternedin or on the semiconductor substrate to form useful devices. The surfaceof the semiconductor device may include the semiconductor material, theinsulator material, and/or the metal.

In an embodiment of the invention, the integrated circuit device isencapsulated in an encapsulating material. As shown in FIG. 1,semiconductor package 100 comprises a semiconductor device 1encapsulated by an encapsulating material 20. Semiconductor device 1typically includes input/output pads 2 at an upper surface ofsemiconductor device 1. A lower surface of semiconductor device 1 isgenerally bonded to a circuit board 10 by an adhesive 3. Circuit board10 generally includes a substrate 15, a circuit pattern 12, and bondfingers 11. Those portions of circuit pattern 12 not covered with bondfingers 11 can be coated with cover coat 16.

Encapsulating material 20 can include a ceramic material or an epoxymaterial. Exemplary thicknesses of the encapsulating material can be inthe range of 1.0×10⁻² mils to 200 mils; 1.0×10⁻² mils to 1.0 mil; and 1mil to 200 mils. Encapsulating material 20 can contact all, or portionsof, semiconductor device 1. Encapsulating material can also encapsulateleads 4, circuit pattern 12, bond fingers 11, and cover coat 16. Incertain embodiments, the leads contacting the semiconductor device maynot be encapsulated.

The encapsulation material can be any resin that can be cured to form aprotective layer over the semiconductor device. Suitable resins includephenolic resins, alkyds, diallyl phthalate resins, polycyanate resins,epoxy resins and the like. Among the suitable epoxy resins are thosebased on bisphenols such as bisphenol A; those based on biphenyl; phenolepoxy novolac resins; cresol epoxy novolac resins; those based ontrisphenol methane derivatives; those based on cyclohexane or otheralicyclic compounds; and the like. Bromine-substituted epoxy resins maybe used to impart flame retardance to the cured resin. The resin canalso be selected together with a curing agent and other additives suchthat upon curing it exhibits a glass transition temperature and heatdistortion temperature. Suitable epoxy formulations are described, forexample, in U.S. Pat. No. 5,232,970 to Solc et al., issued Aug. 3, 1993,incorporated in its entirety herein by reference.

Other epoxy resins may include for example:

-   -   (a) EOCN1020-55, an o-cresol novolac epoxy resin produced by        Nippon Kayaku Co., Ltd. (epoxy equivalent, 200)    -   (b) YX400000HK, a biphenyl epoxy resin produced by Yuka Shell        Epoxy (epoxy equivalent, 190)    -   (c) NC-3000P, an epoxy resin of formula (1) produced by Nippon        Kayaku Co., Ltd. (epoxy equivalent, 272)

Curing Agents:

-   -   (d) DL-92, a phenolic novolac resin produced by Meiwa Kasei        Industries, Ltd. (phenolic hydroxy equivalent, 110)    -   (e) MEH-7800SS, a phenolic aralkyl resin produced by Meiwa Kasei        Industries, Ltd. (phenolic hydroxy equivalent, 175)    -   (f) MEH-7851 L, a phenolic resin of formula (2) produced by        Meiwa Kasei Industries, Ltd. (phenolic hydroxy equivalent, 199).

In an embodiment of the present invention, the encapsulation materialmay further comprise a plurality of nanoparticles. The nanoparticleshave a coefficient of thermal expansion, positive or negative. Invarious embodiments, the nanoparticles can have a coefficient of thermalexpansion similar to that of the bulk material that make-up thenanoparticles. Nanoparticles are added to the encapsulation material toadjust TE_(EM).

Exemplary nanoparticle materials having a positive TE include singleelements, such as the Group IV elements, metals or the rare earthelements. Other nanoparticle materials having a positive TE includenitrides, oxides, phosphides, carbides, sulfides, or selenides, orcombinations thereof. In certain embodiments, the nanoparticle materialscan be metal oxides including titanium dioxide (TiO₂), magnesium oxide(MgO), yttria (YtO), zircronia (ZrO₂), CeOx, alumina (Al₂O₃), lead oxide(PbOx), silica, SiO₂, SiON, or composites of these oxides. In otherembodiments, the materials can be made from III-V compounds or II-VIcompounds. The nanoparticle materials can also include zinc selenide(ZnSe), zinc sulfide (ZnS), and alloys made from Zn, Se, S, Si, Fe, C,B, BN, and Te. Further, the nanoparticle materials can be galliumnitride (GaN), AlGaN, silicon nitride (Si₃N₄), SiN, or aluminum nitride.The material of the nanoparticles can also be metallic elements, suchas, for example, Ag, Al, Au, Co, Cu, Fe, Mo, Ni, and W, and alloysthereof. The material of the nanoparticles can also be non-metallicelements. Exemplary non-metallic elements include, for example, Si andC, in any of their various forms (e.g., diamond, graphite, nanofibers,and single and multi-walled nanotubes). Other types of nanotubes canalso be used.

Exemplary nanoparticle materials having a negative TE include, forexample, Ni—Ti alloys, ZrW₂O₈, ZrMo₂O₈, Y(WO₄)₃, V doped ZrP₂O₇, ZrV₂O₇,ZnW, NaTi₂, (Zr₂O)(PO₄)₂, Th₄(PO₄)₄P₂O₇, and AOMO₄, where A=Nb or Ta,and M=P, As, or V. When nanoparticles having a negative TE are combinedwith a matrix material having a positive TE, the resulting compositematerial may include little or no expansion or contraction even whencycled through various thermal environments. The TE of the resultingcomposite material can be controlled to an extent by the doping level ofthe nanocomposite within the matrix material.

In certain embodiments of the present invention, the TE of the materialsmaking up the nanoparticles is less than TE_(EM). Combining thenanoparticles with the encapsulation material, which can form acomposite, reduces the overall TE of the composite. Additionally, byadding various amounts of nanoparticles having a negative TE and/oradding various amounts of nanoparticles having a positive TE to theencapsulation material, TE_(EM) can be adjusted to closely matchTE_(SD). The nanoparticles reduce or eliminate stress and otherdetrimental effects of TE mismatch.

The nanoparticles can also be dispersed throughout the encapsulationmaterial so that the TE_(EM) is globally affected, making the TE_(EM)uniform throughout. Further, because of the small size of thenanoparticles, stress does not arise within the encapsulation material.In an embodiment of the invention, TE_(EM) can be adjusted to be within20%, 10%, 5%, 1%, or less than 1% of TE_(SD).

The nanoparticles used in the embodiments described herein can besubstantially spherical. Alternatively, the shape of the nanoparticlescan be non-spherical. For example, the shape of the nanoparticles can befaceted or they can assume geometrical shapes such as cubes, pyramids,triangles, trapezoids, parallelograms, hexagons, tubes, or they can haveno defined shape. Moreover, the nanoparticles used in the embodimentsdescribed herein do not need to have the same shape.

The nanoparticles used in the embodiments described herein can be ofvarious sizes. For example, the average size of the nanoparticles can beless than about each of the following: 90 nm, 75 nm, 50 nm, 25 nm, 15nm, 10 nm, 5 nm, 2 nm, 1 nm, or less than 1 nm.

In certain embodiments, nanoparticles are included into the materialmaking up the encapsulation material at a wt % of less than 50 wt % ofthe composites described herein. Alternatively, nanoparticles areincluded into the materials making up the encapsulation material at a wt% of less than 70 wt % of the composites described herein.

In some embodiments, the nanoparticles are not in physical contact witheach other in a host material and are prevented from agglomerating.Agglomeration is understood to be when two or more nanoparticles comeinto physical contact. When any of the nanoparticles are in physicalcontact with another nanoparticle, the two or more nanoparticlesessentially become a single nanoparticle having a size of the combinedtwo or more nanoparticles.

In certain embodiments, the nanoparticles are separated from each otherby the host material. For example, FIG. 2A shows an exemplary section200 of an encapsulation material 220. As seen in FIG. 2A, encapsulationmaterial 220 includes a plurality of nanoparticles 225. In the exemplarysection 200, nanoparticles 225 are separated by encapsulation material220.

In other embodiments, the nanoparticles are prevented from agglomeratingby coating the nanoparticles with a coating. As shown in FIG. 2B, thereis an exemplary section 200 of encapsulation material 220. As seen inFIG. 2B the encapsulation material 220 includes a plurality ofnanoparticles 225 coated with a coating 230. The coating prevents thenanoparticles from agglomerating or flocking together. In an embodiment,the anti-agglomeration coating is a surfactant organic coating.Alternatively, the anti-agglomurant can be any other known organiccoating with anti-agglomurant properties.

The integrated circuit device may be encapsulated by a resin transfermolding process. In this process, a powder or palletized, normally soliduncured resin formulation is heated to a temperature at which it willflow under pressure, and then transferred under pressure to a moldcavity which contains the integrated circuit device. Powders or pelletsmay contain the nanoparticles or the nanoparticles may be combined withthe powder or pellets with heating.

An alternative method is to inject a liquid resin formulation into amold via an autodispensing process. In this process, the resin, curingagent, nanoparticles and other components are formulated so as to beflowable at room temperature (about 25 degrees C.). This flowablemixture is then injected into a mold cavity containing the integratedcircuit device, where it is cured via the application of heat. In thismethod, the resin formulation can be prepared and frozen in a syringe.While frozen, the resin does not cure. This enables the resin to betransported and thawed at the time of use.

Other liquid thermosetting resin formulations may also be used, such asthe “Blop-Top” encapsulants and other liquid epoxy systems as are usedas underfills in flip chip bonding. These resin formulations, whenfilled with nanoparticles can also be used as die attach adhesives.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

1. An integrated circuit device comprising: a semiconductor device; anencapsulant material encapsulating at least a portion of thesemiconductor device, the encapsulant material comprising a plurality ofnanoparticles, wherein the plurality of nanoparticles comprise amaterial selected from at least one of materials having a positivecoefficient of thermal expansion and materials having a negativecoefficient of thermal expansion, and wherein the content ofnanoparticles in the encapsulant material is between about 1×10⁻⁴ and5×10¹ parts per weight.
 2. An integrated circuit device according toclaim 1, wherein the plurality of nanoparticles are coated with ananti-agglomurant.
 3. An integrated circuit device according to claim 1,wherein a mean particle diameter of the plurality of nanoparticles isfrom about 1 to 90 nm.
 4. An integrated circuit device according toclaim 1, wherein the plurality of nanoparticles are selected fromoxides, nitrides, and sulfides.
 5. An integrated circuit deviceaccording to claim 1, wherein the thermal expansion of the encapsulantis within ±20% of the thermal expansion of the surface of thesemiconductor device.
 6. An integrated circuit device according to claim1, wherein the plurality of nanoparticles comprise a material having apositive coefficient of thermal expansion.
 7. An integrated circuitdevice according to claim 6, wherein the plurality of nanoparticles areselected from at least one of titanium dioxide (TiO₂), magnesium oxide(MgO), yttria (YtO), zirconia (ZrO₂), silicon oxide (SiO_(x)), CeO_(x),alumina (Al₂O₃), lead oxide (PbO_(x)), carbon nanotubes, a composite ofyttria and zirconia, gallium nitride (GaN), silicon nitride, aluminumnitride, zinc selenide (ZnSe), zinc sulfide (ZnS), an alloy comprisingZn, Se, S, and Te (Tellurium), nanofibers, single and multi-wallednanotubes.
 8. An integrated circuit device according to claim 1, whereinthe plurality of nanoparticles comprise a material having a negativecoefficient of thermal expansion.
 9. An integrated circuit deviceaccording to claim 8, wherein the plurality of nanoparticles areselected from at least one of Ni—Ti alloys, ZrW₂O₈, ZrMo₂O₈, Y(WO₄)₃, Vdoped ZrP₂O₇, ZrV₂O₇, (Zr₂O)(PO₄)₂, ZnW, NaTi₂, Th₄(PO₄)₄P₂O₇, andAOMO₄, where A=Nb or Ta, and M=P, As, or V.